The most significant voices for liberty of conscience and freedom of religion in the period emerged in England during the Puritan Revolution (1640-1660). Though the three kingdoms of the British Isles—England, Scotland and Ireland—witnessed political and military conflict, a struggle that ensued from the collapse of the rule and religious policies of Charles I, one of the byproducts was a vigorous debate on the principle of toleration. The Lord Protector Oliver Cromwell attempted to bring about toleration for many persecuted Protestant sects. He also granted toleration and readmission of the Jews into England; they had been expelled by royal edict in 1290.
The emergence of democratic or "Leveller" ideas in the Puritan army in the mid- 1640s was accompanied by the clearest articulation of the argument for religious toleration and freedom of conscience. One of the most original of the Levellers was William Walwyn whose numerous works argued against a state church and advocated liberty of conscience for all religions.
Another Leveller leader was Richard Overton, who demanded religious liberty for all of England, including Catholics and Jews. Overton called for the release of the oft-imprisoned activist John Lilburne, who held that religious dissention was the work of the devil and the only path toward peace and harmony was through granting complete freedom of conscience.